I haven't yet had a chance to play with that board, but I can tell you now that your goals are quite achievable.

Leaving the stock multiplier is going to make things simpler overall. Personally I think you'd be better off going with a lower RAM frequency (MHz), tighter timings, and keeping the RAM in a 1:1 ratio with the front side bus of your processor. The stock FSB of a Conroe CPU is going to sync up with DDR2-533, so that's what you're going to set in the BIOS. Then go up in slow steps until you reach the desired speed (in your case 3.0GHz). Boot into Windows and make sure it's stable by running Orthos (google it), in Blend for 24 hours. You can also try some of the other programs in our troubleshooting essentials section.

That is a very good power supply, and will definitely not hold your overclock back.

I'm using the OCZ Gold XTC myself right now, and it's very respectable RAM. Not much good for going past DDR2-800, but you won't be doing that. You'll be running it at DDR2-750, and maybe you can tighten up the timings a bit, but don't get your hopes up too high about that. I've found that RAM doesn't like votage above 2.1V, and it loses stability any higher than that (for me anyway).

You can PM me, or post in this thread for any more help. it'll be easier to help you once your system arrives though :)